There is a need for a sensing system to monitor applied forces and torques. An example of such a sensor system is described in U.S. Pat. No. 3,921,445 to Hill and Sword. In that specification, the manipulator is of a hand-like form comprising a pair of jaws, which are relatively pivotally movable under operation of an electric motor. The manipulator includes a wrist. Sensing means are provided for sensing the magnitude and direction of applied forces and torques. The applied force is decomposed into components corresponding to three mutually orthogonal axes intersecting at the wrist. The sensing means include a series of sensors, extending around the longitudinal axis of the manipulator.
To date, torque and force converters have been largely limited to sophisticated computer applications and have generally been prohibitively expensive for general computer use. In particular, prior art force converters have high manufacturing costs because of the sensing mechanisms and construction requirements that are necessary.
U.S. Pat. No. 4,811,608 issued Mar. 14, 1989, Force and Torque Converter, is hereby incorporated by reference.
Joysticks, track balls, and mice are commonly used to convert a manual motion into an electronic representation to be used by the computer system. Frequently, these devices are employed as pointing instruments to move a cursor or otherwise manipulate a graphical image on the computer screen.
There are two major types of prior art mice: the mechanical mouse, and the optical mouse. Both types are displacement sensing devices. As such, both types have the disadvantage in that they must frequently be lifted and reoriented to allow further movement. For example, the user's range of comfortable motion is often reached before the user is finished "dragging" a graphical object across the screen. Consequently, the user must stop the operation and lift and reorient the mouse, before resuming the desired task. In addition, small work space environments exacerbate this annoying feature, as there is less space in which to displace the mouse.
Besides these ergonomic disadvantages, mechanical mice require regular cleaning and can slip during operation. This results in inconsistent operation. Most optical mice require an optical pad to operate.
Furthermore, computer types, such as lap tops and notebook computers, are gaining increasing acceptance. These computer types have the potential to operate with extremely limited working space requirements, e.g., while a user is seated on an airplane or a train. However, as just discussed, prior art mice do not readily lend themselves to limited working space environments and thus are unamenable to these computer types. This is unfortunate as "mice" are preferred input devices.
Alternative, relatively stationary input devices, such as track balls and joysticks, have been tried. These devices usually sense either the displacement of the apparatus, e.g., joystick, or a velocity component of the device, e.g., track ball. Though these devices do not require large work spaces, they have numerous disadvantages.
To begin with, the software industry has developed software, for the most part, utilizing mouse-functionality as a de facto standard. For example, popular windowing packages exploit mouse-functionality in the well-known "click and drag" feature. In this feature, the user moves the pointer to a desired menu displayed on the screen; the user then depresses a button to display/select the menu; the user, while still depressing the button, then moves the pointer, until the desired menu option is highlighted; the user then releases the button to activate the option.
A mouse implements this in an ergonomically-acceptable fashion. The user needs only one hand to perform the operation of moving the mouse and depressing and releasing the buttons. Moreover, he can use his ergonomically-preferred fingers, i.e., index and middle fingers, to operate the device and, therefore, attain high accuracy yet comfortable movement.
In contrast, the alternative input devices are awkward devices for these type of graphical operations and ergonomically-disadvantageous to use. A track ball and joystick require the user to use two hands, one hand to move the pointer by displacing a joystick or rolling the track ball, and another to activate the buttons. Alternatively, the user can attempt using just one hand to operate the device and activate the buttons, but this requires the user to use ergonomically-disfavored fingers, e.g., the thumb must be used to either roll the ball or operate buttons. To begin with, users prefer to use one hand when performing graphical input operations. In addition, ergonomically-disfavored fingers do not perform precise operations well. Further, joysticks have an inherent difficulty in placing the buttons sufficiently proximate for use.
Similar difficulties are experienced with popular editing packages and other software.
Further, most existing computer input devices are displacement or velocity sensing devices, not force sensing. It is believed that users prefer to have the sensitivity characteristics of the input device (e.g., precision and quickness of pointer movement) change in relation to the applied force and not in relation to displacement. Though it is recognized that some force and torque converters have been used, these are costly and therefore limited to relatively sophisticated systems.
The dynamics of a displacement sensing device depend on many inputs. Two different applied forces can result in the same velocity or displacement of the device depending on these other input variables, such as the weight of a user's hand. Thus, there is no functional relationship between the displacement and the applied force. Consequently, it is extremely difficult, if not impossible, for a displacement sensing device to implement desirable sensitivity characteristics relating the applied force to the output of the apparatus.
Lastly, existing mice, track balls, and joysticks provide limited information to the computer systems. The planar translational movement of the device is usually decomposed into an X component and a Y component (X and Y being orthogonal axes within the sensed plane). Track balls perform an analogous decomposition of the angular movement of the ball. The decomposed information is then used by the computer system to manipulate a pointer or similar graphical object. Consequently, only two basic pieces of information are generally provided, the X component and the Y component, thus offering only two degrees of programming freedom for the applications developer. If the device could sense a rotational component about an axis, in addition to sensing the planar components, a third degree of programming freedom could be offered to applications developers. This additional degree of freedom could then be utilized to add functionality to the applications.